It is already known practice to use a mobile device (smart card or cell phone), to access and/or start up a motor vehicle. The access and/or start-up authorization is given by the vehicle following a question/answer exchange between the vehicle and the mobile device. Conventionally, this exchange of data is performed by radiofrequency (RF) communication, low frequency (LF), Bluetooth, Wi-Fi, NFC (Near Field Communication) type.
For security reasons, the near field communications are preferred because they require the mobile device and the vehicle to be in immediate proximity to one another (distance less than 10 cm). This short distance is an a priori guarantee of enhanced security. This is because, by proceeding in this way, the possibility of the mobile device being spoofed is avoided, because, for that, it would be necessary to introduce a fraudulent element between the mobile device and the vehicle, which could not fail to draw the attention of the legitimate owner of the vehicle.
However, it so happens that, when the legitimate owner of the vehicle is far away from the vehicle, if an ill-intentioned person has, close to the vehicle, a first fraudulent electronic communication device and a second fraudulent communication device close to the legitimate owner, the information requested by the vehicle could be relayed by the two fraudulent electronic devices to the mobile device of the legitimate owner, even though the latter is a long way away from his or her vehicle. Because of this, an authorization to access and/or start up the vehicle could take place, in the absence of and unnoticed by the legitimate owner, even by using a so-called “near field” communication mode.
In practice, the fact that the mobile device of the owner of the vehicle uses a near field communication (NFC) does not provide protection from an ill-intentioned person managing to place a fraudulent communication device in proximity to the latter. Thus, for example, if the owner of the vehicle has a cell phone in his or her pocket and is approached (sufficiently close) by an ill-intentioned person also having a cell phone in his or her pocket, there could be an exchange of data between the two telephones without the legitimate owner noticing it. The very short distance necessary for a near field communication is not therefore totally sufficient to guarantee the inviolability of the communications between a vehicle and a device for accessing and/or starting up this vehicle.